Resumen:

Powder injection moulding is a mature manufacturing process used for mass producing small size and complex geometry components. It is a competitive and effective alternative to the forging and casting methods as it produces near net shape components with a lowPowder injection moulding is a mature manufacturing process used for mass producing small size and complex geometry components. It is a competitive and effective alternative to the forging and casting methods as it produces near net shape components with a low raw material consumption. Thus it is even more effective with expensive materials. The expansion of the PIM requires extensive research in new materials but also of the manufacturing process itself.
The PIM process employs debinding and sintering methods with high time and energy consumption. The environmental awareness of both industrials and customers is pushing for a reduction of these conditions. Within the PIM process, there are two possibilities to find alternatives. One of those would consist to find alternatives to the equipment and methods employed at the moment.
This PhD thesis studied the replacement of the debinding and sintering methods by unconventional one with better kinetics. The supercritical fluid debinding, the FAHP sintering and the microwave sintering are three methods developed for faster performances and were applied to PIM components in order to reach at least the same results as the conventional methods.
This project was developed in collaboration with industrials interested on the elaboration of Inconel 718 parts. The scope of this work is the study and the comprehension of the behaviour of these components while they are treated with these three unconventional methods. With regard to this matter, the formulation and the elaboration of the components is first introduced. Different feedstocks with different powder morphology, a spherical and an irregular flake shape were used. A PP based binder and a CAB based binder were also used. Hence, the homogeneity, the optimum powder volume loading, the thermal and rheological behaviour of both the raw materials and mixtures were all determined in order to perform the tests with the best starting conditions.
The first chapter of this thesis introduces the superalloys and more precisely the nickel-chrome superalloys. The composition, the microstructure and the thermal behaviour of the Inconel 718 was thoroughly investigated. It is followed by an introduction to the powder metallurgy, the MIM process and the research performed on Inconel 718 MIM components. The final part of this chapter presents the three new unconventional methods.
The second chapter presents the raw materials used during this work and their characteristics. The methods employed to obtain the different mechanical, thermal and chemical properties are also introduced. The following chapter presents the results of the application of the conventional MIM process on the MIM components. The first step is the progressive extraction of the polymers composing the binders with first a water debinding step of the PEG followed by a thermal degradation of the remaining organic compounds. The brown part is then sintered via a furnace and a thermal treatment of the metallic compound is concluding the process. All of the steps are optimized in order to reach the best performances of the material.
The next chapter introduces the supercritical fluid debinding method in order to replace the water extraction. The equipment and the methods are presented with the objectives to extract all of the PEG introduced during the elaboration of the feedstock. The quality of the final component is characterized by its surface roughness.
The FAHP sintering and the thermal treatment were performed on fully debinded Inconel 718 MIM components. The methods needed an adaptation to the MIM component and the material in order to avoid geometry deformation and microstructure pollution. The effects on the final components, its mechanical performances and its microstructures, were investigated in order to understand the effects of the method on the MIM components.
The last chapter presents the results observed during the microwave irradiation of the Inconel 718 components. A second method, using a plasma microwave flame, was used to perform thermal treatments on the components. The results on the microstructure and the mechanical performances were investigated via nano-identation tests.[+][-]